Application of atmospheric cold plasma for inactivation of foodborne enteric pathogens on cantaloupe melon and whole raw carrots
Date
2022-12
Authors
Ali, El-sadig
Major Professor
Advisor
Mendonca, Aubrey
Fortes DaSilva, Paulo
Brehm-Stecher, Byron
Committee Member
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Abstract
Rising consumer demand for minimally processed, nutritious fruits and vegetables devoid of treatment with heat or synthetic chemicals has increased the food industry’s interest in “clean” non-thermal food processing technologies including high hydrostatic pressure, pulsed electric fields, and atmospheric cold plasma. Minimally processed fresh and fresh-cut produce are ready-to-eat (RTE) products that receive no further kill step beyond surface washing and sanitizing treatments applied to the whole (uncut) product. Harsh antimicrobial treatments such as very high heat or ionizing radiation can destroy sensitive nutrients or beneficial bioactive compounds in fresh produce. Chemical antimicrobial treatments are limited in the extent of microbial inactivation on the surfaces of whole fresh produce. This problem is further exacerbated when the rough surfaces of certain produce items including cantaloupe melon and raw carrots protect pathogens from chemical sanitizing treatments such as chlorine solutions. Pathogens that survive such treatments can be transferred to the flesh of those products during peeling, cutting, and slicing processes that produce popular convenience type, fresh-cut fruits and vegetables. Within the past decade, the number of associated foodborne illness involving consumption of fresh-cut produce has increased. Those particularly at risk include the immunocompromised, the elderly, infants, and pregnant women. Therefore, effective alternative methods that would inactivate pathogens without altering produce quality, are needed. Non-thermal processing methods are becoming widely popular as decontamination options for fresh produce due to their ability to preserve important sensory and nutritional quality of foods while effectively inactivating pathogenic and spoilage microorganisms. High voltage atmospheric cold plasma (HVACP) is one novel non-thermal method that uses atmospheric air and pressure to facilitate the inactivation of foodborne pathogens. A study was conducted to evaluate the effectiveness of dielectric barrier discharge HVACP for killing two human enteric pathogens namely, Salmonella enterica and shiga toxin-producing Escherichia coli (STEC) on cantaloupe melon rind and on raw carrots. Those two products were inoculated with the pathogens, packaged in sealed rigid polypropylene containers, and exposed to HVACP generated at 60 kV (for carrots), or 80 kV (for melon rind) at set time intervals. Control samples were not treated with HVACP. Control and HVACP-treated samples were retained in their packages at room temperature for 1 h or 24 h post treatment before determining numbers of pathogen survivors. Results indicated that for both produce items, populations of pathogens declined with increased exposure to HVACP. For cantaloupe rind, greater reductions in numbers of pathogens occurred at 24 h compared to1 h post treatment. There were no significant differences in the death rate between the two pathogens irrespective of the product treated with HVACP. Significant numbers sub-lethally injured pathogens were among survivors on melon rinds at 1h but not at 24 h post-HVACP (80 kV) treatment. Similarly, for carrots, significant numbers of sub-lethally injured survivors were not detected at 24 h post HVACP treatment. The results of the present study indicate that dielectric discharge HVACP has good potential as a non-thermal alternative for inactivating pathogens on the outer rind surface of cantaloupe melon and on raw carrots. Moreover, holding those fresh produce items at room temperature for 24 h after HVACP treatment can increase the inactivation of pathogens.
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